The prior art in this respect includes especially chronographs which have a fly back hand function. In this case the fly back hand mechanism is generally used to temporarily stop the timer hand during the timing process, while the measurement process continues in order to allow it to then jump to the measured total time. This is for example the case in order to allow reliable reading of intermediate times while the measurement of the end time continues for the time being. Usually either the normal time display is omitted in these watches, the watch thus being purely a timer, or the timing function is implemented in a separate auxiliary display. Thus, in many applications, the desired information must first be laboriously computed from the information of the normal time display and the measurement of the auxiliary display, and it is usually not possible to directly read the absolute time of the start or end of an event.
Therefore there are also watches with normal analog time indication, which have additional hands which can be moved to a desired position at a certain instant and then directly indicate the relationship and the time difference from the current time.
The document U.S. Pat. No. 1,790,359 describes for example a device by means of which a watch with conventional time indication by means of minute and hour hands can be equipped with additional minute and hour hands in order to indicate the time difference between the instant of the start of an event and the current time. The additional minute and hour hands are manually set in this case, therefore the position of the additional minute and hour hands is always stationary as long as they are not manually moved. The use of such a manual device is obviously tedious, time-consuming and disruptive in normal reading of the time.
U.S. Pat. No. 5,255,248 describes a watch with the same purpose, i.e. a watch which simultaneously allows both normal time indication and also the measurement of a time difference, which is therefore neither a timer nor a completely normal watch, but integrates the two functions in one display. The means which are used for this purpose and primarily the manner of operation are different here.
The watch which is proposed in this patent on the one hand has one additional minute hand which is located coaxially to the hands of the normal time display and which can be moved out of a stationary normal position into the current position of the normal minute hand by actuating a pushbutton. There it remains stationary again in order to mark the start of an event. The step of setting of the additional hand to the current time can be carried out according to the document by means of a conventional fly back hand mechanism.
On the other hand, the described watch has a ring with a marking and a scale which can be turned coaxially around the dial in order to mark for example the end of the event and thus to integrate a “count-down” function.
While this watch thus simultaneously allows normal time indication and also the measurement of the time difference, a fly back hand mechanism for moving the additional minute hand being proposed, the reading of the corresponding displays is not optimum to the extent that the additional minute hand as mentioned has only stationary positions and therefore quite adversely affects the reading process of normal time indication when its time measurement and marking function is not being used. Namely, this hand remains in the position in which it was used last and therefore is continually visible on the dial as a disruptive element.